The proposed research consists of six experimental studies of the similarities and differences in naming impairment, demonstrated by the confrontation naming performance of individuals who have aphasia and those who have Alzheimer's disease (AD). The underlying motivation for the studies is that although both groups show impaired naming abilities in conversation and in formal testing, their difficulties largely result from distinctive underlying impairments. In the proposed studies, these underlying impairments have been dichotomized in accordance with Shallice's model of semantic impairments, i.e., those that result from a degraded semantic store and those that are deficiencies in the ability to access the underlying concepts. We hypothesize here that AD naming problems result from the former, aphasic problems from the latter. The proposed studies explore confrontation naming in these groups of patients in relation to Shallice's characteristics of degraded store and access deficits. The purpose of the research is to provide comparative information about naming deficits that might inform theories of word retrieval, and possibly, to help in the generation of valid rationales for training individuals with naming impairments.